Radiolabeled polyclonal and monoclonal antibodies have been used as reagents for diagnostic tumor imaging and as therapeutic agents. As monoclonal antibodies exhibiting better specificity for tumors become available, they are being evaluated for clinical usefulness in diagnosis and radiotherapy of cancer. These procedures require radiolabeled antibodies. Apart from Technetium 99m labeling, techniques for radiolabeling antibody and other protein are often complicated and dangerous and therefore not regularly used in nuclear medicine practice.
Recently, bifunctional chelates have been used to label antibodies with .sup.111 In or .sup.67 Ga for radio-immunoscintigraphy. In most instances, however, .sup.123 I and .sup.131 I remain the radioisotopes of choice for this application. For persons performing the procedure, radioiodination of protein presents several safety hazards. These include direct radiation exposure and potential thyroid accumulation of radioiodine.
Another problem associated with radioiodination procedures is that radioiodinated antibodies lose immunochemical reactivity due to chemical or radiation damage. Radiation damage is worse for antibody labeled to high specific activity. Thus, to retain immunological reactivity of an antibody, the iodination procedure should be mild to minimize damage of the antibody by chemical reagents and it must be performed shortly before using the antibody to minimize damage of the antibody by radioactive decay.
To achieve widespread use of radiolabeled antibody for clinical applications convenient, rapid and safe radiolabeling procedures are needed.